Investigation Of The Selected Benzophenone Compounds Using Time-Resolved Resonance Raman Spectroscopy And DFT Calculations

The meta-substituted benzophenone compounds can undergo some "meta-effect"photochemical reactions,including photoredox,meta-methyl activation and photosubstitution reactions.In recent years,meta-substituted benzophenone derivatives have been studied in depth.The combination of time-resolved spectroscopy and density functional theory calculations is the main method.The photochemical reaction mechanism of benzophenone derivatives that contain one electron donating or one electron withdrawing group have already been known.However,what is the photochemical reaction of such benzophenone derivatives when the two substituents are introduced and one is an electron-donating and one is an electron-withdrawing group?In this paper,3-fluoro-3 '-hydroxymethy lbenzophenone(compound 1)and 3-fluoro-3 '-methy lbenzophenone3-fluoro-3'-methy lbenzophenone(compound 2)were explored to study the problem.Both compound 1 and compound 2 introduce two groups at the meta-position,.The fluorine atom is a strongly electron-withdrawing group,and the hydroxymethyl group and the methyl group are electron donative groups.In this paper,the photophysical and photochemical processes of compound 1 and compound 2 were studied by means of time-resolved spectroscopy and density functional theory calculations.The main contents of this paper are as follows:(1)The photophysical and photochemical processes of compound 1 were explored.In acetonitrile solution,compound 1 undergoes a typical photophysical process of benzophenone compounds.In the isopropanol solution,compound 1 undergoes a hydrogenation abstraction reaction.In the acidic aqueous solution,compound 1 undergoes photoredox reaction,and the photolysis product is purified and the nuclear magnetic resonance spectrum of the product is obtained.It is found that the stronger the acidity,the higher the reaction efficiency.DFT calculation shows that the transition energy of the photosubstitution reactions is higher,which means that the photoredox reduction reaction is more likely to occur than the photosubstitution reaction.(2)The photophysical and photochemical processes of compound 2 were explored.In acetonitrile solution,compound 2 undergoes a typical photophysical process of benzophenone compounds.In the isopropanol solution,compound 2 undergoes a hydrogenation abstraction reaction.In the acidic aqueous solution,compound 2 undergoes a side chain methyl activation reaction,and the photolysis product is purified and the nuclear magnetic resonance spectrum of the product is obtained.DFT calculation shows that the transition energy of the photosubstitution reactions is higher,which means that the methyl activation reaction is more likely to occur.(3)3-Hydroxymethyl-3'-methoxybenzophenone was synthesized and characterized by 1H-NMR.Solutions of 3-hydroxymethyl-3'-methoxybenzophenone and 3-methy-3'-methoxybenzophenone was prepared in a pH 0 aqueous solution of acetonitrile(volume ratio,1:1).Time-resolved Raman spectroscopy experiments were carried out,but we did not find a meta-effect reaction.